Process for the manufacture of insulator heads



G.IC.NECK

' Jan. 25, 1938.

Filed March 12, 1936 Patented Jan. 25, 1938 rnoonssron' THE'MANUFACTURE' OF IN- MSIULATOR HEADS Gust av 0. Neck, Nossebro,-Sweden,

Application March 12, 1936,--seria1Nm tsgssv 1? In Sweden May 10, 1935 1Claim.

This invention relates to such insulators for electric high tensionmains which consist of a porcelain cup mounted within a cup shaped metalhead which is to be suspended on the pole by means of a hook attached toa dome like hollow projection on the top of the steel head. Theinvention has for its main object to provide an improved process of andapparatus for manufacturing such metal heads of malleable steel.

A further object of the invention is to enable the manufacture of metalheads from flat plates of uniform thickness by a forging process inwhich the portions of the head adapted to sustain a substantial load aregiven a greater thickness than the remaining portions.

Hitherto it has been customary to manufacture such insulator heads fromtempered cast iron, but such members are likely to crack and wearespecially in the top dome where the suspension hook is attached. Tomake the heads of malleable steel in the usual way presents thedifficulty of applying the top dome otherwise than by welding which,however, will increase considerably the manufacturing costs.

In the accompanying drawing an insulator head of the class to bemanufactured by the improved process is illustrated diagrammatically inthe way of example so as to facilitate the understanding of theinvention, wherein Figure 1 illustrates the first stage of the improvedprocess of manufacture, and

Figure 2 the process when completed before the finishing operations areundertaken.

In the drawing I designates a mandrel, the outer configuration of whichcorresponds to the shape of the cavity of the cup head when completed.The mandrel I is supported by a table 2 of a forging press, theconstructive details of which are not shown, because they may be of anywell known design such as easily understood by everybody skilled in theart. Above the mandrel I there is shown in Figure 1 a die 3, the cavityof which corresponds substantially with the outer shape of the insulatorhead to be forged out in the press. To produce the outer form of the topdome I I of the insulator head (Figure 2), the cavity of the die 3consists in a wider lower space 4 provided for the cup shaped main body9 of the insulator head, and in a constricted upper space 5 provided forthe top dome I I. The man drel I has such a low height in relation tothe depth of the cavity 4 of the die that when the die comes to restwithin the mandrel at the end of the forging process, the rounded upperend 6 of the mandrel lies below the entrance to the con- ,stricted upperspace of the cavity in the die 3 as visible in Figure 2. The upper endof the mandrel has an upwardly projecting central point I. The bottom ofthe upper constricted space 5 of the cavity in the die 3 consists, inthe embodi-- ment illustrated, of a removable plug I2 which e TENTOFFICE.

is screwed into a threaded central hole in the body portion of themandrel I should havev a slightly conical shape and that the radius I3of curvature at the top of the mandrel be less than the radius I4 ofcurvature of the corresponding surface of the cavity in the die. It isalso neces sary that the radius I5 of curvature of the die surfacebetween the upper and the lower spaces 5 and 4 of the cavity in the diebe rather large.

I will now describe the improved process of manufacture. I take a flatsteel plate 8, preferably circular in configuration, and of a thicknessof some two and a half times the thickness wanted in the lowerrelatively thin portion of the cupshaped body 9 of the finishedinsulator head. This plate I heat to a high forging temperature andplace it on the top of the mandrel as shown in Figure 1, a small cavityin the lower surface of the plate 8 cooperating with the point I on themandrel to center the blank. Now I make the die 3 descend,compressing-the blank 8 between the walls of the wider cavity space 4and the mandrel I. Owing to the conical form of the mandrel I theinterspace between the mandrel and the walls of the cavity space 4 willdiminish downwards as the die 3 descends, thus more firmly compressingthe blank near the lower end than farther above and causing a firmclamping of the material of the lower end of the blank and forcing theoverflow material upwards towards the upper part of mandrel I and cavityspace 4 and further upwards into the constricted space 5. On account ofthe reduced height of the mandrel, it does not enter the space 5 and thesurplus material of the blank which has been pushed into will be a cupshaped member the shell 9 of which increases in thickness from the lowerend towards the dome portion II the walls of which latter have still agreater thickness than the main body of the cup.

It will be understood that the undermost edge portions I! of the cup areto be removed when the forging is finished, and the die elevated,

and the cup removed from the mandrel.

Notwithstanding I have spoken of the manufacture of insulator heads thisinvention is not limited to such specialties, but can be favourably usedin the manufacture of other objects of similar character.

What I claim is:

A process for the manufacture of a malleable cup-shaped member having adome like hollow top 'main body of the cup-shaped member and providedwith walls and bottom of greater thickness than the initial thickness ofthe blank as well as of the main body of the cup-shaped member.

GUSTAV C. NECK.

